There actually can be bs from a manufacturer where a site cannot list an item below their MSRP so in order to do a sale they have to do the bs like “add to cart to see price” or making you sign in. Sure sometimes it’s not an amazing deal but it can often be the lowest price you can find an item because they aren’t allowed to advertise a price that low.
Edit: See comment below to learn about MAP “minimum advertised price” which is different from MSRP “manufacturer suggested retail price” leaving my above comment alone with its inaccuracy so that the below comment continues to make sense and you can learn as I did.